1. Field of the Invention
The present invention relates to an apparatus for determining quality of a weld bead, especially, a laser weld bead.
2. Description of the Prior Art
Different metal sheets are laser-welded into one-piece assemblies which are then stamped to be used for automobile panels. The weld beads of the assemblies require inspection along the entire weld line to assure that the weld beads have sufficient strength for pressing along with configurations which will not damage the press rolls. To decrease the time period taken in inspection, it has been desired to mechanize the inspection.
Japanese Patent Publication SHO 49-39445 discloses an apparatus with a slit beam of light illuminating a weld bead (arc-weld bead) to make an illuminated band on the surface of the weld bead, photographing the illuminated band by a television camera to make a photograph plane including an image of the illuminated band, and determining the quality of the weld bead based on the image. The technique of using a slit beam of light for detection is also disclosed in Japanese Patent Publication SHO 51-95866.
However, in the conventional apparatus, the image is treated as two-dimensional data, and the entire photograph plane will possess about sixty thousand elements that have to be scanned horizontally and vertically to acknowledge the image. If such an image determination is incorporated into a personal computer for weld bead inspection, the inspection speed (speed of the camera moved along the weld bead) will be too low or the sampling pitch will be too coarse. As a result, an on-line and real-time inspection will be impossible.